Linear motors are used in a variety of electrical devices. For example, linear motors are used in exposure apparatuses for semiconductor processing, other semiconductor processing equipment, elevators, electric razors, machine tools, machines, inspection machines, and disk drives.
Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage retaining a reticle, a lens assembly and a wafer stage retaining a semiconductor wafer. The reticle stage and the wafer stage are supported above a ground with an apparatus frame. Typically, one or more linear motors precisely position the wafer stage and one or more linear motors precisely position the reticle stage. The images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise relative positioning of the wafer and the reticle is critical to the manufacturing of high density semiconductor wafers.
A typical, linear motor includes a magnet assembly that generates a magnetic field and a coil assembly that is positioned near the magnet assembly. The coil assembly includes one or more coils which are individually supplied with an electrical current. Electrical current in the coils interacts with the magnetic field of the magnet assembly. This causes one of the assemblies to move relative to the other assembly. The assembly that moves can be secured to one of the stages, while the other assembly is secured to the apparatus frame. With this design, the stage moves in concert with one of the assemblies relative to the apparatus frame.
Unfortunately, reaction forces transferred to the apparatus frame from each linear motor can deflect the apparatus frame and influence the positions of the stages. This reduces the accuracy of the exposure apparatus and degrades the quality of the semiconductor wafer. Thus, it is often desirable to transfer the reaction forces directly to the ground with a separate reaction frame or to a reaction mass.
Additionally, depending upon the illumination source, the performance of exposure apparatus can be enhanced by controlling the environment around one or both stages. One way to control the environment around a stage is to position a chamber around the stage. Subsequently, the desired environment can be created within the chamber around the stage. However, with the chamber, it is difficult to transfer the reaction forces from the linear motor to the ground or to a reaction mass.
In light of the above, it is an object of the present invention to provide a motor combination that encloses and positions a stage for an exposure apparatus. Another object of the present invention is to couple a linear motor through a chamber so that the reaction forces from the motor can be transferred outside the chamber. Yet another object of the present invention is to couple a motor through a chamber without compromising the seal of the chamber. Still another object of the present invention is to provide an exposure apparatus capable of manufacturing high density semiconductor wafers.